There are several ways to build solid walls using just mud or clay

Question

There are several ways to build solid walls using just mud or clay, but the most extensively used method has been the forming of bricks out of mud or clay, and, after some preliminary air drying or sun drying, they are laid in the wall in mud mortar.

Option AOption BOption COption DOption E

(This question is from Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)

Solution

Sentence Analysis

There are several ways to build solid walls using just mud or clay, (First independent clause. Subject - "ways"; Verb - "are")

but the most extensively used method has been (Second independent clause. Subject - "method"; Verb - "has been")

the forming of bricks out of mud or clay, (first part of the method)

and

, after some preliminary air drying or sun drying, (additional information in double comma)

they are laid in the wall in mud mortar. (second part of the method)

The sentence talks about the most popularly used method to build walls using just mud or clay. The most popular method consists of two things: forming bricks out of mud or clay and laying them in the wall in mud mortar (after some preliminary air or sun drying).

The error in the sentence is lack of parallelism. The two parts of the method are not presented in a parallel structure. “the forming of bricks…” is not parallel to the clause “they are laid…”.

Option Analysis

(A) Incorrect. For the error mentioned above.

(B) Incorrect. The verb-ing “forming the mud…” is not parallel to infinitive “to lay them”.

(C) Incorrect. For the following reasons:

“having bricks formed” is not parallel to the clause “they were laid”.

The use of simple past “were laid” to describe a method that is still used is incorrect.

(D) Correct. The two parts of the process are parallel (“to form” and “to lay”).

(E) Incorrect. For the following reasons:

The use of simple past “were formed” and “were laid” is incorrect since the method is still used.

“which” refers to the closest noun “mud or clay”, leading to an illogical meaning that “mud or clay” was laid in the wall.

Since “which” refers to ‘mud or clay’, “which” is singular (“or” doesn’t make a plural subject out of two singular nouns; only “and” does). Therefore, the use of plural “were laid” is incorrect.

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